This clinical trial was a phase I trial that studied the safety of a commercial preparation that contains hydroxycitrate (HCA). The effect of an escalating dose of HCA on human subjects was studied in a randomized, double-blind, placebo-controlled trial. The study population was healthy but obese men and women older than 21 years recruited from the Johns Hopkins and Baltimore communities. We selected 24 healthy but obese men and women between the ages of 21 and 65 with body mass index (BMI) greater than 28, where BMI=weight in kilograms divided by the square of height in meters, or BMI=weight/height-square (kg,msquare). During the screening visit, subjects were informed about HCA and the risks and benefits of the trial. Subjects signed an informed consent form. Subjects were examined and blood and urine was collected for analysis. Subjects were excluded if they had a history of serious diseases, or any laboratory abnormalities during the screening visit. The 24 subjects were divided into 4 groups of 6 subjects each. In each group, 2 of the 6 subjects were randomly assigned to receive placebo, and 4 of the 6 subjects were randomly assigned to receive HCA for a total of 28 days. The first group of 6 received the lowest dose of HCA or placebo for 28 days. Then the next group received the intermediate dose for 28 days. Then the third group received the highest dose of HCA. Then the fourth group received the highest dose of HCA. The subjects returned to clinic each week of the study for a history, physical examination, and blood and urine analysis. The low dose of HCA was 333 mg PO TID for a total of 1 g daily (1.2 mmole TID for 3.6 mmole daily total). The intermediate dose of HCA was 666 mg PO TID for a total of 2 g daily (2.5 mmole TID for a total of 7.5 mmole daily). The high dose of HCA was 1332 mg PO TID for a total of 4 g daily (5 mmole TID for a total of 15 mmole daily). The entire protocol was completed in January through September, 1996. No adverse reactions were observed in the subjects taking HCA, but 2 adverse reactions were observed in subjects taking placebo. The average weight loss for the HCA group was 0.5 kg, and the average weight loss for the placebo group was 2 kg. We conclude that HCA is safe at the maximum dose tested. We are currently designing a double-blind placebo-controlled Phase II trial of the efficacy of HCA.